Center for Economic and Social Research, University of Southern California, 635 Downey Way, VPD, Los Angeles, CA, 90089, USA.
Leonard Davis School of Gerontology, University of Southern California, Los Angeles, United States.
BMC Public Health. 2024 Oct 5;24(1):2720. doi: 10.1186/s12889-024-20101-y.
High body-mass index (BMI) is an established risk factor for late-life cognitive impairment and dementia, but most evidence comes from high-income contexts. Existing evidence from cross-sectional data in low- and middle-income settings is inconsistent, and many studies do not adequately address potential sources of bias.
We used data from Wave 1 of the Longitudinal Aging Study in India (LASI) (analytic N = 56,753) to estimate the association between BMI categories and cognitive functioning among older adults aged 45 + years using survey-weighted linear regression models stratified by gender and controlling for potential confounders including demographic factors, socio-economic status (SES) characteristics, and health-related behaviors. To probe potential sources of bias, including residual confounding and reverse causation, we used weighting and trimming methods, sample restriction, and explored effect modification.
In fully adjusted models, relative to normal BMI underweight BMI was associated with lower cognitive scores (Men: -0.16 SD difference, 95% CI -0.18, -0.13; Women: -0.12 SD, -0.15, -0.10). Overweight and obesity were associated with higher cognitive scores in both men (overweight: 0.09; 0.07, 0.12, obese: 0.10; 0.05, 0.15) and women (overweight: 0.09; 0.07-0.12, obese: 0.12; 0.08-0.15). Estimates were similar after weighting and trimming but were attenuated after excluding those with low cognition (≥1 SD below the mean relative to those with similar demographic characteristics). Positive associations between overweight and obese BMI and cognition were attenuated or null in those living in urban settings and those with higher levels of educational attainment.
Underweight BMI is a risk factor for poor cognitive outcomes in adults 45 years and older and may be indicative of poor nutritional status and life-course disadvantage in India. In tandem with existing literature, supplemental analyses and effect modification results indicate that unmeasured confounding and reverse causation may explain the observed positive associations between overweight and obese BMI and cognitive functioning from cross-sectional studies in low- and middle-income settings. Future data with longitudinal follow-up will be helpful to further disentangle biases.
高体重指数（BMI）是导致晚年认知障碍和痴呆的既定风险因素，但大多数证据来自高收入环境。来自低收入和中等收入环境的横断面数据的现有证据并不一致，许多研究没有充分解决潜在的偏倚来源。
我们使用印度纵向老龄化研究（LASI）第 1 波的数据（分析 N=56753），使用调查加权线性回归模型，按性别分层，并控制包括人口统计学因素、社会经济地位（SES）特征和健康相关行为在内的潜在混杂因素，估计 BMI 类别与 45 岁及以上成年人认知功能之间的关联。为了探究潜在的偏倚来源，包括残余混杂和反向因果关系，我们使用加权和修剪方法、样本限制，并探索了效应修饰。
在完全调整的模型中，与正常 BMI 相比，低体重 BMI 与较低的认知评分相关（男性：-0.16 SD 差异，95%CI -0.18，-0.13；女性：-0.12 SD，-0.15，-0.10）。超重和肥胖与男性（超重：0.09；0.07，0.12，肥胖：0.10；0.05，0.15）和女性（超重：0.09；0.07-0.12，肥胖：0.12；0.08-0.15）的较高认知评分相关。加权和修剪后估计值相似，但在排除认知水平较低（与具有相似人口统计学特征的人相比，认知水平低于平均值 1 个标准差）的人后，估计值减弱。在城市居住者和教育程度较高的人群中，超重和肥胖 BMI 与认知之间的正相关减弱或变为无效。
低体重 BMI 是成年人（45 岁及以上）认知不良结局的危险因素，可能表明印度的营养状况不佳和人生历程中的劣势。与现有文献一起，补充分析和效应修饰结果表明，来自低收入和中等收入环境的横断面研究中观察到的超重和肥胖 BMI 与认知功能之间的正相关可能是由未测量的混杂因素和反向因果关系引起的。未来具有纵向随访的数据分析将有助于进一步厘清偏差。
